Cause of oyster illness remains a mystery

BATON ROUGE, La. — Louisiana health officials are still trying to determine what’s led to a stomach illness outbreak that forced the closure of three oyster harvest areas in the past two weeks.

The areas in St. Bernard, Plaquemines, and parts of Lafourche and Jefferson parishes have been closed to oyster fishing as a precaution.

The disease, norovirus, is a more common and much less serious oyster-related sickness than the bacterial vibrio vulnificus disease that prompted the Food and Drug Administration to flirt with restrictions on raw oysters last fall.

The symptoms of norovirus — fever, chills, aches, nausea, and diarrhea — can last up to two days.

“It’s certainly not a bad virus, but it’s one that gets everybody’s attention,” said Jimmy Guidry, state health officer with the Louisiana Department of Health and Hospitals.

As of last week, 38 cases of norovirus in Mississippi and the New Orleans area were tied to oysters from the three separate zones in Louisiana waters.

Eleven people got sick near Pascagoula after eating oysters at a seafood-related conference at the Grand Bay National Estuarine Research Reserve; another 13 got sick at a wedding in New Orleans.

Although DHH has confirmed that everyone who was sick had eaten oysters, Guidry said it’s still unclear whether the problem was related to contamination in the water where oysters were harvested or if someone handling them passed on the virus.

Norovirus is highly contagious and can be transferred from someone who has the virus onto the raw shellfish, or to another person through human contact.

DHH has tested the water in the three zones for fecal coliform, often present in sewage and human waste, but found nothing. Sometimes the virus can get into the oysters if boats dump waste overboard in a harvest area.

The Plaquemines beds will remain closed through Thursday, and the St. Bernard grounds through next week. The oyster grounds near Grand Isle in Lafourche and Jefferson parishes are still under investigation because DHH officials believe the problem may be confined to one specific harvest area.

Industry officials say the closures have not markedly affected the supply of oysters.

John Tesvich, a co-owner of AmeriPure Oysters in Franklin who chairs the state’s oyster task force, said the supply is still brisk but that the number of closures has been unusual this year.

“It happens annually in some areas of the country, and unfortunately we’ve had more than our share this year,” Tesvich said. “We expect everything to be back to normal in the next couple weeks.”